Reaction injection molding (RIM) is a versatile process by which elastomeric parts can be fabricated. The RIM process involves high pressure impingement mixing of a polyisocyanate stream (A-side) and an active hydrogen containing, isocyanate-reactive stream (B-side) followed by immediate injection into a closed mold. The primary appeal of this process lies in its inherently high productivity. One factor which limits productivity, however, is the ease of demolding the elastomeric parts. On the one hand, the system must cure fast enough for good green strength at demold while on the other it must not be so fast that large complicated molds cannot be filled. Ease of removal of the part from the mold is also important and is related to green strength as well as mold release agent used. Many internal mold release agents have been devised which provide ease of release at the expense of system reactivity, either making it more difficult to fill large molds or causing less than desirable green strength within acceptable demold times. In addition to system reactivity problems from internal release agents, inert inorganic fillers which are commonly used in elastomeric RIM systems for automotive applications can also cause brittleness or cheesiness at demold.
The B-side of elastomeric RIM systems is normally composed of a blend of a high molecular weight polyether polyahl for the soft block, a diol or diamine chain extender for the hard block and additives such as surfactants, flame retardants, catalysts and internal release agents. When the polyether is OH-terminated, such as a 6000 molecular weight triol, tin and tertiary amine catalysts are generally used.
In order to improve the properties of such RIM elastomers at demold, several approaches have been taken:
U.S. Pat. No. 4,433,067 discloses the use of polyether polyamines in place of the polyols, resulting in polyurea RIM systems which require no tin or amine catalysts.
U.S. Pat. No. 4,444,910 discloses the use of tin and amine catalysts in the aforementioned polyurea system for improved green strength.
U.S. Pat. No. 4,546,114 discloses the use of mold temperatures about 110.degree. C. for improved green strength in polyurea systems.
U.S. Pat. No. 4,983,643 discloses the use of polyester-modified isocyanate prepolymers in the A-side of polyurea systems for reduced brittleness at demold.
U.S. Pat. No. 4,595,743 discloses the use of low molecular weight amine-initiated polyols as additives to these systems for higher crosslinking and improved green strength.
The use of low molecular weight, amine-initiated polyols is fairly well-known in the polyurethane industry for such applications as rigid foam. In addition, the use of fatty aminopolyols has been disclosed previously.
U.S. Pat. No. 4,696,771 discloses the synthesis of fatty amino polyols bearing a single tertiary amine group from the reaction of N-substituted ethanolamines with glycidyl ethers of fatty alcohols or glycidyl esters of fatty acids.
U.S. Pat. No. 4,897,428 discloses the use of specific fatty aminopolyols as compatibilizers for zinc laurate or zinc oleate in RIM as internal mold release agents.
U.S. Pat. Nos. 4,764,540 and 4,789,688 disclose the use of fatty aminopolyols bearing ether, ester and/or amide groups in RIM formulations for improved release.
U.S. Pat. No. 4,374,222 discloses the use of fatty amide-based polyols in polyurethanes as internal mold release agents.
U.S. Pat. No. 3,065,247 discloses the reaction of polyamines with equimolar amounts of epoxidized fatty acid esters of lower alcohols. An example would be butyl epoxy-stearate. These products are distinguished from those of the present invention in that: (1) they use equimolar amounts of reactants and therefore do not react all of the available NH groups; and (2) the fatty chains attached in the ring-opening reaction are attached at the middle instead of the ends. The products of U.S. Pat. No. '247 are described as useful as emulsifying agents in petroleum products and as corrosion inhibitors. Polyurethane applications are not mentioned.
U.S. Pat. Nos. 4,764,540; 4,789,688 and 4,847,307 disclose the use of imidazolines to neutralize highly acidic silicone internal mold release agents.
U.S. Pat. No. 5,076,989 discloses the use of imidazolines to compatibilize zinc stearate, laurate and oleate for purposes of internal mold release agents in RIM.
U.S. Pat. Nos. 4,886,838 and 5,019,600 discloses the use of salts of imidazolines with carboxylic acids to compatibilize zinc stearate, laurate and oleate as internal mold release agents in RIM.